if you bridge an amp, and it says say 300 watts rms to one at 4 ohms and you hook it up to a four ohm subwoofer, thats 300watts rms... right ok, so now if you add another woofer, and leave the amp bridged, are the subwoofers now getting 150 watts a piece or are they both seeing 300 watts? My friend and I have been arguing about this all week.
First of all, an amp that's 4ohms stable bridged, will give you the rated power at that ohm only. So for your example, yes you will get 300w rms @ 4ohms. However, if you add another 4ohms sub to it, now you've dropped the amp's ohm to 2ohms. It will now produce almost 2x more power at the same time burning out. You have to be very careful not to exceed the amp's minimum ohm limit. If you remember the ohm's law, anything connected in parallel, will divide the power in half. So 300w will become 150w x 2. Your subs will see 150w each.